Douglas Nowacek

Research

North Atlantic right whale (Eubalaena glacialis) in the
Bay of Fundy, Canada. This picture shows the front of the
upper and lower jaw as the whale approached the camera.

One focus of my current research is the effect(s) of anthropogenic noise on marine mammals. Many species of marine mammals can potentially be affected by anthropogenic noise in the ocean, and we are studying the acoustic, behavioral, and, soon, some physiological responses of the animals to this noise. One of the species we're studying is the North Atlantic right whale, which is not only affected by noise but also by interactions with ships. Several whales are hit and killed each year, so we are working to assess the risk factors contributing to those collisions. The tag we use also records the motor behavior of the tagged animal, e.g., fluke stroke rate. From these data we are looking at swimming and diving behavior, hydrodynamics (e.g., drag), and eventually energetics. Recent articles, "Whales Drawn to Emergency Sirens" by Paul Rincon with BBC News and "Alarm Sirens Lure Whales Into Peril" by NewScientist.com highlight this research.

This spectrogram shows a sound produced by a right whale that was tagged with a digital acoustic recording tag. Time in seconds is on the x-axis and frequency in kHz is shown on the y-axis. The whales make several different types of sounds, often during social interactions.

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Florida manatee (Trichechus manatus) mother and calf.

Florida manatees are also involved in interactions with vessels. In fact, each year more than 100 manatees are killed by boat strikes in Florida and many more are hit but not killed! Blunt trauma and direct propeller injuries are almost equally responsible for manatee deaths. We know that many animals are hit and not killed because the vast majority of Florida manatees have scars from past collisions. In addition to studying manatee interactions with boats, we are also studying their vocalizations. Recently we published a paper in the Journal of the Acoustical Society of America comparing vocalizations of Florida manatees with manatees in Belize. For all of this work we use a combination of methodologies including tagging, passive acoustic recording, behavioral observations from boats and/or video cameras, and still photography for photo-identification.

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A bottlenose dolphin (Tursiops truncatus) in Sarasota Bay
is shown here eating a mullet. Dolphins chase and eat individual prey,
and we study the behavioral and acoustic sequences leading to those captures.

Photo courtesy of the Sarasota Dolphin Research Program

One of my specific areas of research is the use of echolocation and foraging behavior in one of the odontocetes, the bottlenose dolphin. Bottlenose dolphin echolocation is a sophisticated tool for target detection, ranging and discrimination. One of the emerging topics in my research is the ecology of dolphins and their prey, specifically the 'arms race' that can develop between a predator using an active sensory system and their prey. In other words, if your prey can hear you coming, the dynamic between predator and prey is completely different than in the case of a surprise attack. Echolocating bats and their prey provide a fascinating model for this research, and since high frequency hearing sensitivity in some fishes has been documented, the conditions exist for an arms race between dolphins and their prey.